Production of isobutylene



Patented Dec. 11, 1945 UNITED STATES PATENT OFFICE PRODUCTION OF ISOBU'I'YLENE Leonard N. Lenin, Upper Darby, and Frank G.

Ciapetta, Yeadon, Pa., asslgnors to The Atlantic Refining Company, Philadephla, Pa., a corporation of Pennsylvania No Drawing.- Application October 7, 1942,

Serial No. 461,236 a 3 Claims, (Cl. 260683) lyst such as an argillaceous adsorbent or a mineral acid such as phosphoric acid.

In the production of various products involving the use of isobutylene it has been found necessary to employ substantially pure isobutylene or a gas containing a high concentration of isobutylene. For example, in the production of butyl rubber by the reaction of isobutylene and butadiene, or in the manufacture of high molecular weight isobutylene polymers as agents for increasing the viscosity index or reducing the 0 pour point of lubricating oils, the isobutylene must be of a relatively high degree of purity. In the production of high antiknock gasoline without the use of tetraethyl lead, i. e., 100 octane gasoline by the hydrogenation of isooctene. the 5 isobutylene utilized in the preparation of the isooctene must be substantially pure.

It has been proposed heretofore to produce substantially pure isobutylene by the sulfuric acid polymerization of a mixture of isobutylene, 3o

butenes, and butane, under such conditions that only th isobutylene was converted to diisobutylene, which was separable from the unpolymerized butenes and butane. The relatively pure diisobutylene was then catalytically or ther- 85 mally depolymerized to isobutylene. Another method proposed for the preparation of isobutylene of high purity was the selective conversion of the isobutylene content of a gaseous hy-' drocarbon mixture to the corresponding alcohol, 40

tiary butyl alcohol as the raw 'material for the manufacture of relatively pure isobutylene.

In accordance with the present invention, we have found that a gas containing a high concentration of isobutylene may be produced from butylene polymers other than dii'sobutylene, without having the isobutylene contaminated with substantial quantities of butenes or butane. In the polymerization of gaseous hydrocarbons with phosphoric acid at elevated temperature for the production of motor fuel components, as disclosed in prior patents to Ipatieif -#1,960,631 and #2,018,066, it has been found that the polymer liquid resulting from the phosphoric acid process codimers, together with relatively small amounts of diisbutylene, butene polymers, and higher molecular weight polymers. butene codimers comprise essentially a mixture of 3,4,4 trimethyl pentene-l; 3,4,4 trimethyl pentene-2; 2,3,4 trimethyl pentene-l; 2,3,4 trimethyl pentene-2; and minor amounts of 2,3,3 trimethyl pentene-l. The butene polymers appear to be predominantly 3,4 dimethyl hexene-l and 3,4 dimethyl hexene-2, while the higher molecular weight polymers may include small amounts of trimers of isobutylene, and of butene- 1 or butene-2.

We have found that thisrelatively complex polymer liquid comprising coaimers, butene polymers, and minor amounts of d'nsobutylene is very satisfactory as a charging stock for the production of a gas containing a nigh concentration of isobutylene, i. e., a concentration of at least percent and preferably at least percent isobutylene.

In accordance with our invention, we subject this polymer liquid to thermal treatment in the presence of a catalyst which may be designated as a depolymerizing catalyst, although it may function additionally as an isomerization agent.

As a result of this treatment, a substantial proportion of the polymer hquid is converted into isobutylene, without the appearance of substantial quantities of butene-1 or butene-2 which might normally be expected as a result of the depolymerization of the isobutylene butene codimers. The isobutylene thus producedinhigh concentration may be separated from unconverted polymer liquid by suitable means, and the latter may be recycled for further conversion.

The thermal treatment in the presence of the catalyst may be carried out at temperatures between 400 F. and 1000 F., and preferably between 400 and 800 F., such temperature varying depending upon the catalyst used. The treatment maybe carried out at subatmospheric, at-

' mospheric, or superatmospheric pressure, and preferably at substantially atmospheric pressure.

Catalysts which may be employed include argillaceous adsorbents such as fullers earth, bentonite, acid activated bentonite or clay, bauxite, activated alumina, oxides or sulfides of metals of groupVI of the periodic system, alkaline earth metal oxides, rare earthoxides, or mineral acids such as phosphoric acid, metaphosphoric acid o pyrophosphoric acid which may or may-not be supported upon carriers such as diatomaceous earth, clay, titania, thoria, or the like. With fullers earth catalyst, temperatures between 600 F. and 700 F. have been found satisfactory, a temperature of about 700 F. being preferred. On the other hand, with a catalyst consists predominantly of isobutylene-butene 60 Such as phosphoric acid deposited n diatoms- The isobutylene- 2 l i 2,890,951 ceous earth, temperatures between 400 F. and suits obtained are presented in the following 700 F. may be utilized, a temperature of about table.

Polymer liquid Polymer liquid Polyma liquid m w Charge:

Volume (0. c. at 60 F.) 1 1 2 1,461 111 6 116 5 116.0. Weights ($1118.). 1113 1,072 86 6 86 1 84.6. ugyrggity (A. P. I.) degrees 60 R 61 1 60 60 68.4.

Fuller's earth--- -Fullar's earth--- H;P0onBiOg.- Fulleraearth-.. Fuller's earth. Vo ume (c c) 30 60 30 30 30. Conditions:

Catalyst temp. F 714 M0 503 702 704. Space velocity 60 l 2.52 2.08 1 06 1.04 1.00 Running time 2 is 2 2 2.

ucts: Liquid: 7

Weight (gma) 68 R 004 M 8 3&2 41.7. gravity (A. P. I.) degrees 67 4 7 0 65 0 68.7 68.7.

Volume (1. 32 F) 11 0 150.7 s a 14 a 12.5. Weight (gms.) 36.4. 886 15.4 as 6 32.1. D ty (gm. 0 32 Fl 2.54--- 2.56 2.58 2.55 2.66. Yields (based on chg.

Liquid weight percent) 61 8 66.3 71 i 44 40.3. Gas (we ght percent) 31.8- 36 0 17 R 42 37.0. YielLoss (weight permnfl o 4 7.7 0 1 1 ds: 4 Mol. percent isobutylene in 0 gas traction-.- 97.3. 04.2.- 90 n 93.2--- 91.2.

' 500 F. being preferred. The rate of charge 'of From the results above given, it will be evident he Poly r liquid to the heated catalyst m y that in accordance with our invention, we are range from 0.5 to 5.0 volumes of polymer liquid able to produce gas containing a high concentra- -per volume of catalyst pe hour. The catalyst; tion of isobutylene from polymer liquids comprisupon becoming spent by reason of the accumuing predominantly isobutylene-butene dimers lation of heavy polymers or carbonaceous maand minor amounts of butene polymers and diterials,-may be regenerated by treatment with isobutylene. In all cases, a concentration or at appropriate solvent or by calcination in the presleast 90 mol. percent of isobutylene was obtained ence of air, or by a combination of such methods. despite the fact that the codimers in the charge In carrying out our conversion process, polyliquid contained 50 percent of normal butene mer liquid consisting predominantly of isobutyiradicals. Furthermore, in the case. of the charge one-butene codimers may be vaporized in a conliquid comprising the polymer fraction having a ventional tubular heater and the vapors then boiling range of 240 F. to 250 F., a gas containbrought into "contact with the catalyst contained ing 91.2 mol. percent of isobutylene was obtained, in a suitable vessel at the desired conversion temalthough 'the polymer fraction charged consistperature. The products from the conversion op- 40 ed predominantly of normal butene polymers, eration comprising isobutylene, unconverted i. e., polymers of butene-l and butene-2. It there- Dolymer liquid, and higher polymers, may be septore appears that the production of high yields of arated by fractionation and the unconverted isobutylene in accordance with our P100858 polymer liquid may be recycled for further treatvo es not only d nolyme izat on but also isomeriment. zation of the hydrocarbons produced by the de- Our invention may be further illustrated by polymerization. V

the following examples, which, however, are not We claim:

to be construed as limiting the scope thereof. 1. The method of producing a gas containing 2200 volumes of fresh charge consisting of 11 isobuty'lene in high concentration from polymer percent is'obutylene, 13 percent normal butenes, liquid consisting predominantly of isobutyleneand 76 percent butane, togethe with 500 volumes butene codimers, which comprises contacting the of recycle butane, was charged per day to a catpolymer liquid with an argillaceous catalyst at a alytic polymerization unit employing phosphoric temperature between 600". F. and 800 F., and

acid deposited on diatomaceous earth. The unit separating the resulting gas containing a high was operated at a temperature of 290 F. to concentration of-isobutylene from the moon-- 330 F. under a pressure of 1050, pounds per vertedpolymerliquid.

quare inch, and therewas produced a polymer 2. The method of producing a gas containing liquid comprising essentially 3.5 percent of di. isobutylene in high concentration from polymer isobutylene (boiling, range 212 F. to 220- F.) ,80 liquid consisting predominantly of isobutylenepercent of isobutylene-butene codimer (boiling butene codimers, which mp115es W range 220 F. to 238 F.) and 17.5 percent of normlymer liquid with a f earth f- 1 It mal butene polymers (boiling range 238' F. to temperature between 600 and EL separating the resulting gas containing a high 7 of 230 F. to 240 F. and consisted of codimers,

In producing a gas having a high concentm concentration 01 isobutylene from the unconverted polyme liquid. tion of isobutylene, the whole polymer liquid was I 1 t I m used in some cases. while in other cases the po y- The method of sing a gas con mer liquid was fractionated to give a plurality minan 180mm, of fractions, each or which was treated se gii e el fi g 5:312 compi i s es ontactim i t e rately. one or h f ti a boilinc r e polymer liquid with a fuller-s earth catalyst at a temperature of about 700 F., and separating the while a second fraction had a boiling range of resulting gas containing at least 90 percent iso- 240' F. to 250 F. and consisted essentially of norbutylene from the unconverted polymer liquid. mal butene polymers. The conditions employed LEONARD N. LEUM.

in the conversion operations, as well as the re-- FRANK G. CIAPE'I'IA.

at-least percent-isobutylene from polymer 

